Systems and Methods for Phase Noise Tracking Reference Signal Sequence Generation Using Demodulation Reference Signals

ABSTRACT

A user equipment ( 910 ) is provided for use in a cellular network. The user equipment includes a transceiver ( 1010 ), a processor ( 1020 ), and a memory ( 1030 ). The user equipment ( 910 ) is configured to determine, for a data transmission, a mapping form a demodulation reference signal (DMRS) to a PNT-RS. A DMRS resulting signal is generated from a subset of DMRS for a first resource element in a subcarrier. The DMRS resulting signal is copied from the first resource element to a second resource element assigned to the PNT-RS in the subcarrier. The data transmission is transmitted using the DMRS resulting signal and the PNT-RS.

PRIORITY

This application claims priority to U.S. Patent Provisional ApplicationNo. 62/292,990 filed on Feb. 9, 2017, entitled “Systems and Methods forPhase Noise Tracking Reference Signal Sequence Generation UsingDemodulation Reference Signals,” the disclosure of which is herebyincorporated by reference.

TECHNICAL FIELD

The present disclosure relates, in general, to wireless communicationsand, more particularly, to systems and methods for Phase Noise TrackingReference Signal (PNT-RS) sequence generation using DemodulationReference Signals (DMRS).

BACKGROUND

Communications between a transmitter and receiver generally require someform of synchronization in time and/or frequency before transmissions ofmessages can be received reliably. In cellular systems, such as LongTerm Evolution (LTE), base stations broadcast narrowband synchronizationsignals regularly in time. These synchronization signals allow wirelessdevices accessing the system to perform an initial cell search. Forexample, wireless devices may go through a synchronization procedurethat includes finding carrier frequency, time reference instants, andcell identity. A LTE wireless device that has performed initial cellsearch and identified the cell identity can then complete the initialsynchronization in downlink by making a fine synchronization on cellspecific reference signals that are transmitted over the systembandwidth and more frequently in time than the synchronization signals.The wireless device connects to the network via a random accessprocedure in which uplink time synchronization will be established andcommunications between the device and the base station can begin. Due tooscillator drifting at both transmitter and receiver sides, the wirelessdevice needs to regularly perform fine frequency synchronization indownlink during the communications with the base station.

A lean frame structure design for NX without cell-specific referencesignals (CRS) has been proposed where instead reference signals requiredfor fine synchronization and demodulation of a downlink (DL) physicaldata channel (PDCH) are embedded into the PDCH transmission. FIG. 1illustrates the DL transmissions of PDCH and associated physicaldownlink control channel (PDCCH), carrying an assignment or a grant.More specifically, FIG. 1 illustrates that the first OrthogonalFrequency Division Multiplexing (OFDM) symbol of a subframe containsPDCCH and following OFDM symbols contain PDCHs.

As also illustrated in FIG. 1, transmissions of PDCH may span overmultiple subframes in the case of subframe aggregation or be confined toone subframe. A wireless device, which may also be referred to as userequipment (UE), detects PDCCH addressed to the UE and derives from thescheduling information PDCH related information. A UE is not aware ofPDCCH transmissions to other UEs where a PDCCH to one particular user iscarried on a subset of OFDM subcarriers. The mapping of PDCCH can eitherbe distributed or localized with latter being illustrated in FIG. 1. Thenumber of OFDM symbols within a subframe is a system design parameterand may very well be larger than the 4 used in the depicted example.

In the illustrated example, PDCCH and PDCH have their own referencesignals for demodulation which mainly refer to Demodulation ReferenceSignals (DMRS) but could potentially also refer to other types ofreference signals as will be discussed herein. The DMRS should betransmitted early in the subframe to enable the receiver to performearly channel estimation and by that reduce receiver processing time.

In the context of NX, time-synchronization is done using a firstreference signal (e.g., a Time Synchronization Signal (TSS)) andcoarse-frequency-sync using the same first reference signal or a secondsignal (e.g., Frequency Synchronization Signal). One may observe thatthese signals are not intended to provide a very accuratesynchronization, neither in time nor in frequency. The time-error can behandled by the cyclic-prefix in an OFDM system and the frequency errorby having sufficient sub-carrier spacing. However, in order to not limitthe performance of higher rank transmissions of PDCH in conjunction withhigher modulation (such as 64 and 256 QAM) schemes, betterfrequency-synchronization is needed. State of the art solutions (e.g. asin LTE) reuse DMRS or CRS for this purpose.

In 5G system deployments at higher carrier frequencies, the radio linkwill exhibit some new properties compared to LTE at lower carrierfrequencies. One of the fundamental changes is that the phase noiseproblem is scaled with frequency which introduces a need for a new phasereference signal to mitigate phase noise that is common for allsubcarriers within an OFDM symbol. This reference signal may be neededboth in uplink and downlink. It is foreseen that this signal can be usedfor both fine carrier frequency-synchronization and phase noisecompensation. Where the second is the focus, the reference signal may bereferred to as the Phase Noise Tracking Reference Signal (PNT-RS).

FIG. 2 illustrates an example time-frequency grids containing DMRS andPNT-RSs. The illustrated design is just one example since the design hasnot yet been specified in 3GPP. As depicted, the reference signal istransmitted time continuously and a length 8 cover-code is assumed to beused to create 8 orthogonal DMRS resources. The DMRS resource can beenumerated 0 . . . 7 and can be considered to be 8 DMRS ports. In theillustrated example, four different PNT-RS are depicted to support fourtransmitters with different phase noise.

The PNT-RS is transmitted jointly with the DMRS. As such, the PNT-RS isalso transmitted jointly with the PDCH on a subset of the subcarriersthat are used to transmit the DMRS. The DMRS is here assumed to betransmitted in one or a few OFDM symbols early within a subframe orwithin a subframe aggregation whereas the PNT-RS may be possiblytransmitted in every OFDM symbol. The density of the DMRS in thefrequency domain is significantly higher than the corresponding densityof the PNT-RS. Thus, the set of subcarriers occupied by DMRS issignificantly higher than the set of subcarriers occupied by the PNT-RS.In contrast to radio channels that are often non-flat over thetransmission bandwidth, the phase ambiguity caused by the phase noisewill impact all subcarriers in a similar way. The reasoning fortransmitting PNT-RS on more than one subcarrier is basically then toobtain frequency diversity as well as increasing the processing gain.

Multi-layer transmissions of PDCH require a set of orthogonal DMRS whichcan be constructed by either interleaved Frequency Division Multiplexing(FDM) or Code Division Multiplexing (CDM) or both. Interleaved FDM orCDM may also be known as combs in LTE. CDM may refer to Orthogonal CoverCodes (OCC) based on, for example, Walsh-Hadamard codes or DFT or anyother schemes that may provide orthogonality in code domain. In certainembodiments, OCC in time domain may be less suitable when phase noiseneeds to be tracked within the subframe. Moreover, DMRS needs to betransmitted in multiple OFDM symbols which may not always be the case inNX. Therefore, if sub-carriers are blocked by PNT-RS, the maximum numberof available DMRS may be limited.

In a traditional synchronized radio system, such as, for example, LTE,some signals are always present to allow the UE to find the signalswithout having to communicate with the network first. Examples of suchsignals include Primary Synchronization Signal (PSS), SecondarySynchronization Signal (SSS), and CRS. These types of signals allow theUE to keep time-frequency sync with the network. However, the always-onsignals add some complexity to the radio system, result in bad energyperformance, and provide constant interference.

Some more recent solutions include a lean system design that removessaid signals. A problem with these designs is that the sync-procedurebecomes more complicated and overhead has increased in terms of PNT-RSsusing a large fraction of the spectrum at the cost of decreased datarates. For example, reusing DMRS is inefficient as the neededtime-density is high for accurate phase noise tracking. The DMRS designtakes frequency selectivity into account implying that the resourcedensity in frequency needs to be rather high for demodulationperformance. Thus, if the same signal is used for both demodulation andphase noise tracking, unnecessary high overhead may be created.

Accordingly, a separate PNT-RS may be used. However, this creates aproblem in that the sub-carriers used for phase noise tracking areblocked as the OFDM symbols used for DMRS also contain phase noise andneeds a phase noise reference. Thus, an early placement of a largernumber of DMRS can be problematic if a large number of orthogonal DMRSare needed with early DMRS.

SUMMARY

To address the foregoing problems with existing solutions, disclosed ismethods and systems for Phase Noise Tracking Reference Signal (PNT-RS)sequence generation using Demodulation Reference Signals (DMRS). Morespecifically, PNT-RS sequences may be generated from the effective DMRSsignal. Accordingly, effective over all layers, the symbol transmittedin the intersection of the PNT-RS and DMRS may be used and copied to allother resource elements assigned to PNT-RS.

According to certain embodiments, a user equipment is provided for usein a cellular network. The user equipment includes a transceiver, aprocessor, and a memory. The user equipment is configured to determine,for a data transmission, a mapping form a demodulation reference signal(DMRS) to a PNT-RS. A DMRS resulting signal is generated from a subsetof DMRS for a first resource element in a subcarrier. The DMRS resultingsignal is copied from the first resource element to a second resourceelement assigned to the PNT-RS in the subcarrier. The data transmissionis transmitted using the DMRS resulting signal and the PNT-RS.

According to certain embodiments, a method by a user equipment in acellular network includes determining, for a data transmission, amapping form a demodulation reference signal (DMRS) to a PNT-RS. A DMRSresulting signal is generated from a subset of DMRS for a first resourceelement in a subcarrier. The DMRS resulting signal is copied from thefirst resource element to a second resource element assigned to thePNT-RS in the subcarrier. The data transmission is transmitted using theDMRS resulting signal and the PNT-RS.

According to certain embodiments, a network node is provided for use ina cellular network. The network node includes a transceiver, aprocessor, and a memory. The network node is configured to determine,for a data transmission, a mapping form a demodulation reference signal(DMRS) to a PNT-RS. A DMRS resulting signal is generated from a subsetof DMRS for a first resource element in a subcarrier. The DMRS resultingsignal is copied from the first resource element to a second resourceelement assigned to the PNT-RS in the subcarrier. The data transmissionis transmitted using the DMRS resulting signal and the PNT-RS.

According to certain embodiments, a method by a network node in acellular network includes determining, for a data transmission, amapping form a demodulation reference signal (DMRS) to a PNT-RS. A DMRSresulting signal is generated from a subset of DMRS for a first resourceelement in a subcarrier. The DMRS resulting signal is copied from thefirst resource element to a second resource element assigned to thePNT-RS in the subcarrier. The data transmission is transmitted using theDMRS resulting signal and the PNT-RS.

According to certain embodiments, a method in a wireless transmitter forgenerating a PNT-RS includes determining a DMRS and a PNT-RS mapping fora data transmission. A DMRS resulting signal is generated from a subsetof DMRS for a first resource element in a subcarrier. The DMRS resultingsignal signal is copied from the first resource element to a secondresource element assigned to the PNT-RS in the subcarrier. The datatransmission is transmitted using the DMRS resulting signal and thePNT-RS.

According to certain embodiments, a wireless transmitter for generatinga PNT-RS includes a transceiver, a processor, and a memory. The wirelesstransmitter is configured to determine a DMRS and a PNT-RS mapping for adata transmission. A DMRS resulting signal is generated from a subset ofthe DMRS for a first resource element in a subcarrier. The DMRSresulting signal is copied from the first resource element to a secondresource element assigned to the PNT-RS in the subcarrier. The datatransmission is transmitted using the DMRS resulting signal and thePNT-RS.

According to certain embodiments, a method in a wireless receiver fortracking PNT-RS includes performing a first channel estimate on a set ofDMRS in a first Orthogonal Frequency Division Multiplexing (OFDM) symbolin a sub-carrier. A first phase noise reference is determined in a firstresource element in the first OFDM symbol in the sub-carrier. A secondphase noise reference is extracted in a second resource element in asecond OFDM symbol in the sub-carrier. A second channel estimate isgenerated by performing a phase noise compensation of the first channelestimate using said first and second phase reference. Data is receivedin the second OFDM symbol using the second channel estimate.

According to certain embodiments, a wireless receiver for tracking phasenoise tracking reference signal (PNT-RS) includes a transceiver, aprocessor, and a memory. The wireless receiver is configured to performa first channel estimate on a set of demodulation reference signals(DMRS) in a first Orthogonal Frequency Division Multiplexing (OFDM)symbol in a sub-carrier. A first phase noise reference is determined ina first resource element in the first OFDM symbol in the sub-carrier. Asecond phase noise reference is extracted in a second resource elementin a second OFDM symbol in the sub-carrier. A second channel estimate isgenerated by performing a phase noise compensation of the first channelestimate using said first and second phase reference. Data is receivedin the second OFDM symbol using the second channel estimate.

Certain embodiments of the present disclosure may provide one or moretechnical advantages. For example, certain embodiments may enable anoverhead reduction and better utilization of resources for DMRS,enabling a high number of DMRS early in a sub-frame even in the presenceof a substantial number of orthogonal PNT-RS. There is no other knownsolution when using all resource elements in an OFDM symbol for DMRSwhile enabling phase noise tracking. Consider, for example, an uplink(UL) (or downlink (DL)) Multi User Multiple Input Multiple Output(MU-MIMO) system with four or more receiver antennas. Therefore, thebenefits of having only DMRS in an OFDM symbol such as better peak toaverage and nice frequency interpolation properties, frequency domaincombs are blocked without the herein disclosed systems and techniques.

Other advantages may be readily apparent to one having skill in the art.Certain embodiments may have none, some, or all of the recitedadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed embodiments and theirfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is block diagram illustrating downlink transmissions of PhysicalData Channel (PDCH) and associated Physical Downlink Control Channel(PDCCH) for carrying an assignment or grant;

FIG. 2 is a block diagram illustrating example time-frequency gridscontaining demodulated reference signals (DMRS) and phase noise trackingreference signals (PNT-RS);

FIG. 3 is a block diagram illustrating an example time-frequency gridincluding copied DMRS symbol for phase noise tracking, in accordancewith certain embodiments;

FIG. 4 is a flow diagram of an example method by a wireless receiver fortracking phase noise using a PNT-RS, in accordance with certainembodiments;

FIG. 5 is a block diagram illustrating an example virtual computingdevice for tracking phase noise, in accordance with certain embodiments;

FIG. 6 is a flow diagram of another example method by a wirelessreceiver for tracking phase noise using a PNT-RS, in accordance withcertain embodiments;

FIG. 7 is a block diagram illustrating another example virtual computingdevice for tracking phase noise, in accordance with certain embodiments;

FIG. 8 is a flow diagram of an example method by a wireless transmitterfor generating PNT-RS, in accordance with certain embodiments;

FIG. 9 is a block diagram illustrating an example virtual computingdevice for generating PNT-RS, in accordance with certain embodiments;

FIG. 10 is a block diagram illustrating an example time-frequency gridincluding phase noise tracking when using length of two Orthogonal CoverCodes (OCC) in time, in accordance with certain embodiments;

FIG. 11 is a block diagram illustrating an embodiment of a network 100for phase noise tracking, in accordance with certain embodiments;

FIG. 12 is a block diagram illustrating an example wireless device forphase noise tracking, in accordance with certain embodiments;

FIG. 13 is a block diagram illustrating an example network node forphase noise tracking, in accordance with certain embodiments; and

FIG. 14 is a block diagram illustrating an example radio networkcontroller or core network node, in accordance with certain embodiments.

DETAILED DESCRIPTION

According to certain embodiments, the Phase Noise Tracking ReferenceSignal (PNT-RS) sequence is generated from the transmitted effectiveDemodulation Reference Signal (DMRS). More specifically, the DMRS symboltransmitted in the intersection of the PNT-RS and DMRS are used andcopied to all other resource elements assigned to PNT-RS. FIG. 3illustrates an example time-frequency grid including copied DMRS symbolfor phase noise tracking. As shown, the PNT-RS 0 is depicted as a copyof the DMRS resource element in the same sub-carrier.

In certain embodiments, the DMRS signal may be copied as the complexvalue transmitted in the resource element. This implies that thereceiver may assume that the signal is a known signal that is copied andtime shifted to the second OFDM symbol. In certain embodiments, thereceiver may assume that the signal is time-continuous. For example,each copy may be shifted with a cyclic prefix (CP) duration such thateach previous copy of the PNT-RS can act as a CP.

Example techniques for phase noise tracking may be implemented by boththe receiver and the transmitter. FIG. 4 illustrates is a flow diagramof an example method 200 by a wireless receiver for tracking phase noiseusing a PNT-RS, in accordance with certain embodiments. In certainembodiments, the wireless receiver may comprise a network node or awireless device, examples of which are described below in more detailwith regard to FIGS. 11-13.

The method begins at step 202 when the wireless receiver determines DMRSand PNT-RS mapping. In certain embodiments, the set of DMRS may includea plurality of resource elements associated with the first OFDM symbol.

At step 204, a first channel estimate is performed on a set of DMRS. Theset of DMRS may include a first resource element used as a first phasenoise reference on a sub-carrier in a first OFDM symbol. Wirelessreceiver may then determine a first phase noise reference in a firstresource element in the first OFDM symbol in the sub-carrier at step206. In certain embodiments, the PNT-RS may be continuous in all OFDMsymbols of the subcarrier.

At step 208, the wireless receiver extracts a second phase noisereference in a second resource element in a second OFDM symbol on thesub-carrier. Using the first and second phase noise reference, a secondchannel estimated may be generated at step 210 by performing a phasenoise compensation of the first channel estimate for said second OFDMsymbol. At step 212, data is received in the second OFDM symbol usingthe second channel estimate.

In certain embodiments, the method for tracking PNT-RS as describedabove may be performed by a virtual computing device. FIG. 5 is a blockdiagram illustrating an example virtual computing device 300 fortracking PNT-RS, in accordance with certain embodiments. As depicted,virtual computing device 300 may include modules for performing stepssimilar to those described above with regard to the method illustratedand described in FIG. 4. For example, virtual computing device 300 mayinclude a first determining module 310, a performing module 320, asecond determining module 330, an extracting module 340, a generatingmodule 350, a receiving module 360, and any other suitable modules fortracking PNT-RS. In some embodiments, one or more of the modules may beimplemented by a processor, such as the exemplary processors describedbelow with respect to FIGS. 12 and 13. Additionally, it is recognizedthat, in certain embodiments, the functions of two or more of thevarious modules described herein may be combined into a single module.

The first determining module 310 may perform certain or all of thedetermining functions of virtual computing device 300. For example, incertain embodiments, first determining module 310 may determine a DMRSand PNT-RS mapping. In a particular embodiment, first determining module310 may receive the DMRs and PNT-RS mapping from a network node. Inanother embodiment, first determining module 310 may acquire the DMRSand PNT-RS mapping from a wireless device.

The performing module 320 may perform the performing certain or all ofthe functions of virtual computing device 300. For example, in certainembodiments, first performing module 320 may perform a first channelestimate on a set of DMRS in a first OFDM symbol in a sub-carrier.

The second determining module 330 may perform certain or all of thedetermining functions of virtual computing device 300. For example, incertain embodiments, second determining module 330 may determine a firstphase noise reference in a first resource element in the first OFDMsymbol in the sub-carrier.

The extracting module 340 may perform certain or all of the extractingfunctions of virtual computing device 300. For example, in certainembodiments, extracting module 340 may extract a second phase noisereference in a second resource element in a second OFDM symbol in thesub-carrier.

The generating module 360 may perform certain or all of the generatingfunctions of virtual computing device 300. For example, in certainembodiments, generating module 360 may generate a second channelestimate by performing a phase noise compensation of the first channelestimate using said first and second phase noise reference.

The receiving module 380 may perform certain or all of the receivingfunctions of virtual computing device 300. For example, in certainembodiments, receiving module 380 may receive data in the second OFDMsymbol using the second channel estimate.

Other embodiments of virtual computing device 300 may include additionalcomponents beyond those shown in FIG. 5 that may be responsible forproviding certain aspects of the receiver's functionality, including anyof the functionality described above and/or any additional functionality(including any functionality necessary to support the solutionsdescribed above). The receiver may include components having the samephysical hardware but configured (e.g., via programming) to supportdifferent radio access technologies, or may represent partly or entirelydifferent physical components than those depicted.

FIG. 6 is a flow diagram of another example method 400 by a wirelessreceiver for tracking phase noise using PNT-RS, in accordance withcertain embodiments. In certain embodiments, the wireless receiver mayinclude a network node or a wireless device, example embodiments ofwhich are described in more detail below with regard to FIGS. 12 and 13.The method 400 begins at step 402 when the wireless receiver determinesa DMRS and PNT-RS mapping.

At step 404, a first channel estimate is performed on DMRS. The DMRS mayinclude a first resource element used as a first phase noise referenceon a sub-carrier in a first OFDM symbol. In a particular embodiment, forexample, wireless receiver may perform a first channel estimate on a setof demodulation reference signals and determine a first phase noisereference in a first resource element in a first OFDM symbol in asub-carrier.

At step 406, a second phase noise reference in a second resource elementin a second OFDM symbol on the sub-carrier is extracted.

At step 408, phase noise compensation of said channel estimate for saidsecond OFDM symbol is performed using the first and second phase noisereferences. For example, wireless receiver may generate a second channelestimate by performing phase noise compensation of the first channelestimate using the first and second phase references.

At step 410, data is received in the second OFDM symbol using the secondchannel estimate.

In certain embodiments, the method for tracking PNT-RS as describedabove may be performed by a virtual computing device. FIG. 7 is a blockdiagram illustrating an example virtual computing device 500 fortracking PNT-RS, in accordance with certain embodiments. As depicted,virtual computing device 500 may include modules for performing stepssimilar to those described above with regard to the method illustratedand described in FIG. 6. For example, virtual computing device 500 mayinclude a determining module 510, a first performing module 520, anextracting module 530, a second determining module 540, a receivingmodule 550, and any other suitable modules for tracking PNT-RS. In someembodiments, one or more of the modules may be implemented by aprocessor, such as the exemplary processors described below with respectto FIGS. 12 and 13. Additionally, it is recognized that, in certainembodiments, the functions of two or more of the various modulesdescribed herein may be combined into a single module.

The determining module 510 may perform certain or all of the determiningfunctions of virtual computing device 500. For example, in certainembodiments, determining module 510 may determine a DMRS and PNT-RSmapping. In a particular embodiment, first determining module 510 mayreceive the DMRs and PNT-RS mapping from a network node. In anotherembodiment, determining module 510 may acquire the DMRS and PNT-RSmapping from a wireless device.

The first performing module 520 may perform certain or all of theperforming functions of virtual computing device 500. For example, incertain embodiments, first performing module 520 may perform a firstchannel estimate on the DMRS. In certain embodiments, the DMRS mayinclude a set or subset of DMRS that includes a first resource elementused as a first phase noise reference on a sub-carrier in a first OFDMsymbol.

The extracting module 530 may perform certain or all of the extractingfunctions of virtual computing device 500. For example, in certainembodiments, extracting module 530 may extract a second phase noisereference in a second resource element in a second OFDM symbol on thesub-carrier.

The second performing module 540 may perform certain or all of theperforming functions of virtual computing device 500. For example, incertain embodiments, second performing module 540 may perform phasenoise compensation of said channel estimate for said second OFDM symbolusing the first and second phase noise references.

The receiving module 550 may perform certain or all of the receivingfunctions of virtual computing device 500. For example, in certainembodiments, receiving module 550 may receive data in the second OFDMsymbol using the second channel estimate.

Other embodiments of virtual computing device 500 may include additionalcomponents beyond those shown in FIG. 7 that may be responsible forproviding certain aspects of the receiver's functionality, including anyof the functionality described above and/or any additional functionality(including any functionality necessary to support the solutionsdescribed above). The receiver may include components having the samephysical hardware but configured (e.g., via programming) to supportdifferent radio access technologies, or may represent partly or entirelydifferent physical components than those depicted.

FIG. 8 is a flow diagram of an example method 600 by a wirelesstransmitter for generating PNT-RS, in accordance with certainembodiments. In certain embodiments, the wireless transmitter mayinclude a network node or a wireless device, example embodiments ofwhich are described in more detail below with regard to FIGS. 12 and 13.The method 600 begins at step 602 when the wireless transmitterdetermines a DMRS and PNT-RS mapping for a data transmission.

At step 604, the wireless transmitter generates a DMRS resulting signalfor a first resource element in a set of DMRS resources in asub-carrier. In certain embodiments, the DMRS resulting signal may be agenerated from a subset of the DMRS that includes at least one DMRS andmay include all of the DMRSs, in a particular embodiment. In certainembodiments, the first resource element may be associated with a firstOFDM symbol and all resource elements associated with the first OFDM maybe used to generate the DMRS resulting signal.

At step 606, the wireless transmitter copies the DMRS resulting signalto resource elements in the associated PNT-RS in the sub-carrier. Incertain embodiments, the wireless transmitter may copy the DMRSresulting signal from a first resource element to at least a secondresource element that is assigned to the PNT-RS in the subcarrier.

In certain embodiments, the PNT-RS may be continuous in all OFDM symbolsin the subcarrier, and the wireless transmitter may copy the DMRSresulting signal to all resource elements assigned to all OFDM symbolsassigned to the PNT-RS in the subcarrier. For example, in a particularembodiment, a complex value may be copied from the first resourceelement to each of the OFDM symbols of the subcarrier mapped to thePNT-RS.

In certain embodiments, the copy from the first resource element may betime-shifted across the subcarrier. For example, where a complex valueis copied from the first resource element to each of the OFDM symbols ofthe subcarrier mapped to the PNT-RS, the complex value may time-shifted.In a particular embodiment, each copy of the complex value across thesub-carrier mapped to PNT-RS may be shifted with a CP duration.

In one particular embodiment, for example, the resulting signal may begenerated using an OCC of a length associated with multiple adjacentOFDM symbols. Copying the first resource element may include, for eachone of the plurality of adjacent OFDM symbols, copying a respective DMRSresulting signal to a respective OFDM symbol.

At step 608, the wireless transmitter transmits the data transmissionwith the DMRS resulting signal and the PNT-RS.

In certain embodiments, the method for generating PNT-RS as describedabove may be performed by a virtual computing device. FIG. 9 is a blockdiagram illustrating an example virtual computing device 700 forgenerating PNT-RS, in accordance with certain embodiments. As depicted,virtual computing device 700 may include modules for performing stepssimilar to those described above with regard to the method illustratedand described in FIG. 8. For example, virtual computing device 700 mayinclude a determining module 710, a generating module 720, a copyingmodule 730, a transmitting module 740, and any other suitable modulesfor generating PNT-RS. In some embodiments, one or more of the modulesmay be implemented by a processor, such as the exemplary processorsdescribed below with respect to FIGS. 12 and 13. Additionally, it isrecognized that, in certain embodiments, the functions of two or more ofthe various modules described herein may be combined into a singlemodule.

The determining module 710 may perform certain or all of the determiningfunctions of virtual computing device 700. For example, in certainembodiments, determining module 710 may determine a DMRS and PNT-RSmapping. In a particular embodiment, first determining module 510 mayreceive the DMRs and PNT-RS mapping from a network node. In anotherembodiment, determining module 510 may acquire the DMRS and PNT-RSmapping from a wireless device.

The generating module 720 may perform certain or all of the generatingfunctions of virtual computing device 700. For example, in certainembodiments, generating module 720 may generate

The copying module 730 may perform certain or all of the copyingfunctions of virtual computing device 700. For example, in certainembodiments, copying module 730 may copy

The transmitting module 740 may perform the transmitting functions ofvirtual computing device 700. For example, in certain embodiments,transmitting module 740 may transmit

Other embodiments of virtual computing device 700 may include additionalcomponents beyond those shown in FIG. 9 that may be responsible forproviding certain aspects of the receiver's functionality, including anyof the functionality described above and/or any additional functionality(including any functionality necessary to support the solutionsdescribed above). The receiver may include components having the samephysical hardware but configured (e.g., via programming) to supportdifferent radio access technologies, or may represent partly or entirelydifferent physical components than those depicted.

In the scenario where the DMRS are generated using Orthogonal CoverCodes (OCC) in time, the generation of phase-reference can be differentfor different layers in the transmission depending on which of the timeOCC codes the different layers are mapped to. In this case, full phasenoise tracking may not be possible. On the other hand, if the phasenoise is dominantly of low frequency, an average over two or moreadjacent OFDM symbols may be used.

FIG. 10 illustrates an example time-frequency grid 800 including phasenoise tracking when using length of two OCC in time, according tocertain embodiments. Specifically, phase noise tracking is performed bycopying the individual signals from the two OFDM-symbols and repeatingthese in every second pair of OFDM symbols for the PNT-RS, as shown.Thus, an average over two adjacent OFDM symbols is used.

Certain of the embodiments provided herein are described as beingapplicable for phase noise compensation. For example, in certainembodiments, the copied DMRS signal can be used to do phase noisecompensation. As the transmission is assumed to be contained within thecoherence time of the channel, the channel response is not changedbetween copies of the DMRS signal. If that is not the case, multipleDMRS can be used and the techniques disclosed herein used multiple timeswithin the same transmission. Since the channel is assumed to not changeduring the transmission time interval, the difference in two copies ofthe DMRS-signal can be assumed to be due to the phase noise variationbetween the two OFDM symbols. As a result, this difference can be usedto compensate the channel estimate.

In a practical implementation, for example, multiple copies of differentcopies of the DMRS-signal may be used with proper filtering to removevariations in interference between the copies. This filter kernel istypically tuned to the channel estimate and the expected frequencyprofile of the phase noise. For example, the filter kernel may usemultiple time instances of the PNT-RS if the phase noise is dominated bylow frequency content and use only a single instance if high-frequencycontent is dominating.

The techniques for tracking phase noise as disclosed herein may beimplemented by a network. FIG. 11 is a block diagram illustrating anembodiment of a network 900, in accordance with certain embodiments.Network 900 includes one or more wireless devices 910A-C, which may beinterchangeably referred to as wireless devices 910 or UEs 910, andnetwork nodes 915A-C, which may be interchangeably referred to asnetwork nodes 915 or eNodeBs (eNBs) 915. A wireless device 910 maycommunicate with network nodes 915 over a wireless interface. Forexample, a wireless device 910A may transmit wireless signals to one ormore of network nodes 915, and/or receive wireless signals from one ormore of network nodes 915. The wireless signals may contain voicetraffic, data traffic, control signals, and/or any other suitableinformation. In some embodiments, an area of wireless signal coverageassociated with a network node 915 may be referred to as a cell. In someembodiments, wireless devices 910 may have D2D capability. Thus,wireless devices 910 may be able to receive signals from and/or transmitsignals directly to another wireless device. For example, wirelessdevice 910A may be able to receive signals from and/or transmit signalsto wireless device 910B.

In certain embodiments, network nodes 915 may interface with a radionetwork controller (not depicted in FIG. 11). The radio networkcontroller may control network nodes 915 and may provide certain radioresource management functions, mobility management functions, and/orother suitable functions. In certain embodiments, the functions of theradio network controller may be included in network node 915. The radionetwork controller may interface with a core network node. In certainembodiments, the radio network controller may interface with the corenetwork node via an interconnecting network. The interconnecting networkmay refer to any interconnecting system capable of transmitting audio,video, signals, data, messages, or any combination of the preceding. Theinterconnecting network may include all or a portion of a publicswitched telephone network (PSTN), a public or private data network, alocal area network (LAN), a metropolitan area network (MAN), a wide areanetwork (WAN), a local, regional, or global communication or computernetwork such as the Internet, a wireline or wireless network, anenterprise intranet, or any other suitable communication link, includingcombinations thereof.

In some embodiments, the core network node may manage the establishmentof communication sessions and various other functionalities for wirelessdevices 910. Wireless devices 910 may exchange certain signals with thecore network node using the non-access stratum layer. In non-accessstratum signaling, signals between wireless devices 910 and the corenetwork node may be transparently passed through the radio accessnetwork. In certain embodiments, network nodes 915 may interface withone or more network nodes over an internode interface. For example,network nodes 915A and 915B may interface over an X2 interface (notdepicted).

As described above, example embodiments of network 900 may include oneor more wireless devices 910, and one or more different types of networknodes 915 capable of communicating (directly or indirectly) withwireless devices 910. Wireless device 910 may refer to any type ofwireless device capable of communicating with network nodes 915 oranother wireless device 910 over radio signals. Examples of wirelessdevice 910 include a mobile phone, a smart phone, a PDA (PersonalDigital Assistant), a portable computer (e.g., laptop, tablet), asensor, a modem, a machine-type-communication (MTC)device/machine-to-machine (M2M) device, laptop embedded equipment (LEE),laptop mounted equipment (LME), USB dongles, a D2D capable device, oranother device that can provide wireless communication. A wirelessdevice 910 may also be referred to as UE, a station (STA), a device, ora terminal in some embodiments. Also, in some embodiments, genericterminology, “radio network node” (or simply “network node”) is used. Itcan be any kind of network node, which may comprise a Node B, basestation (BS), multi-standard radio (MSR) radio node such as MSR BS,eNode B, network controller, radio network controller (RNC), basestation controller (BSC), relay donor node controlling relay, basetransceiver station (BTS), access point (AP), transmission points,transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS),core network node (e.g. MSC, MME etc), O&M, OSS, SON, positioning node(e.g. E-SMLC), MDT, or any suitable network node.

The terminology such as network node and UE should be consideringnon-limiting and does in particular not imply a certain hierarchicalrelation between the two; in general “eNodeB” could be considered asdevice 1 and “UE” device 2, and these two devices communicate with eachother over some radio channel. Example embodiments of wireless devices810, network nodes 815, and other network nodes (such as radio networkcontroller or core network node) are described in more detail withrespect to FIGS. 12, 13, and 14, respectively.

Although FIG. 11 illustrates a particular arrangement of network 900,the present disclosure contemplates that the various embodimentsdescribed herein may be applied to a variety of networks having anysuitable configuration. For example, network 900 may include anysuitable number of wireless devices 910 and network nodes 915, as wellas any additional elements suitable to support communication betweenwireless devices or between a wireless device and another communicationdevice (such as a landline telephone). Furthermore, although certainembodiments may be described as implemented in a LTE network, theembodiments may be implemented in any appropriate type oftelecommunication system supporting any suitable communication standardsand using any suitable components, and are applicable to any radioaccess technology (RAT) or multi-RAT systems in which the wirelessdevice receives and/or transmits signals (e.g., data). For example, thevarious embodiments described herein may be applicable to LTE,LTE-Advanced, LTE-U UMTS, HSPA, GSM, cdma2000, WiMax, WiFi, anothersuitable radio access technology, or any suitable combination of one ormore radio access technologies. Although certain embodiments may bedescribed in the context of wireless transmissions in the downlink, thepresent disclosure contemplates that the various embodiments are equallyapplicable in the uplink and vice versa.

FIG. 12 is a block schematic of an example wireless device 910, inaccordance with certain embodiments. As depicted, wireless device 910includes transceiver 1010, processor 1020, and memory 1030. In someembodiments, transceiver 1010 facilitates transmitting wireless signalsto and receiving wireless signals from network node 915 (e.g., via anantenna), processor 1020 executes instructions to provide some or all ofthe functionality described above as being provided by wireless device1010, and memory 1030 stores the instructions executed by processor1020.

Processor 1020 may include any suitable combination of hardware andsoftware implemented in one or more modules to execute instructions andmanipulate data to perform some or all of the described functions ofwireless device 1010. In some embodiments, processor 1020 may include,for example, one or more computers, one or more central processing units(CPUs), one or more microprocessors, one or more applications, and/orother logic.

Memory 1030 is generally operable to store instructions, such as acomputer program, software, an application including one or more oflogic, rules, algorithms, code, tables, etc. and/or other instructionscapable of being executed by a processor. Examples of memory 1030include computer memory (for example, Random Access Memory (RAM) or ReadOnly Memory (ROM)), mass storage media (for example, a hard disk),removable storage media (for example, a Compact Disk (CD) or a DigitalVideo Disk (DVD)), and/or or any other volatile or non-volatile,non-transitory computer-readable and/or computer-executable memorydevices that store information.

Other embodiments of wireless device 910 may include additionalcomponents beyond those shown in FIG. 11 that may be responsible forproviding certain aspects of the wireless device's functionality,including any of the functionality described above and/or any additionalfunctionality (including any functionality necessary to support thesolution described above).

FIG. 13 is a block schematic of an example network node 915, inaccordance with certain embodiments. Network node 915 may be any type ofradio network node or any network node that communicates with a wirelessdevice 910 and/or with another network node. Network nodes 915 may bedeployed throughout network 900 as a homogenous deployment,heterogeneous deployment, or mixed deployment. A homogeneous deploymentmay generally describe a deployment made up of the same (or similar)type of network nodes 915 and/or similar coverage and cell sizes andinter-site distances. A heterogeneous deployment may generally describedeployments using a variety of types of network nodes 915 havingdifferent cell sizes, transmit powers, capacities, and inter-sitedistances. For example, a heterogeneous deployment may include aplurality of low-power nodes placed throughout a macro-cell layout.Mixed deployments may include a mix of homogenous portions andheterogeneous portions.

As depicted, network node 915 may include one or more of transceiver1110, processor 1120, memory 1130, and network interface 1140. In someembodiments, transceiver 1110 facilitates transmitting wireless signalsto and receiving wireless signals from wireless device 110 (e.g., via anantenna), processor 1120 executes instructions to provide some or all ofthe functionality described above as being provided by a network node915, memory 1130 stores the instructions executed by processor 1120, andnetwork interface 1140 communicates signals to backend networkcomponents, such as a gateway, switch, router, Internet, Public SwitchedTelephone Network (PSTN), core network nodes or radio networkcontrollers, etc.

In certain embodiments, network node 915 may be capable of usingmulti-antenna techniques, and may be equipped with multiple antennas andcapable of supporting Multiple Input Multiple Output (MIMO) techniques.The one or more antennas may have controllable polarization. In otherwords, each element may have two co-located sub elements with differentpolarizations (e.g., 90 degree separation as in cross-polarization), sothat different sets of beamforming weights will give the emitted wavedifferent polarization.

Processor 1120 may include any suitable combination of hardware andsoftware implemented in one or more modules to execute instructions andmanipulate data to perform some or all of the described functions ofnetwork node 915. In some embodiments, processor 1120 may include, forexample, one or more computers, one or more central processing units(CPUs), one or more microprocessors, one or more applications, and/orother logic.

Memory 1130 is generally operable to store instructions, such as acomputer program, software, an application including one or more oflogic, rules, algorithms, code, tables, etc. and/or other instructionscapable of being executed by a processor. Examples of memory 1130include computer memory (for example, Random Access Memory (RAM) or ReadOnly Memory (ROM)), mass storage media (for example, a hard disk),removable storage media (for example, a Compact Disk (CD) or a DigitalVideo Disk (DVD)), and/or or any other volatile or non-volatile,non-transitory computer-readable and/or computer-executable memorydevices that store information.

In some embodiments, network interface 1140 is communicatively coupledto processor 1120 and may refer to any suitable device operable toreceive input for network node 915, send output from network node 915,perform suitable processing of the input or output or both, communicateto other devices, or any combination of the preceding. Network interface1140 may include appropriate hardware (e.g., port, modem, networkinterface card, etc.) and software, including protocol conversion anddata processing capabilities, to communicate through a network.

Other embodiments of network node 915 may include additional componentsbeyond those shown in FIG. 13 that may be responsible for providingcertain aspects of the radio network node's functionality, including anyof the functionality described above and/or any additional functionality(including any functionality necessary to support the solutionsdescribed above). The various different types of network nodes mayinclude components having the same physical hardware but configured(e.g., via programming) to support different radio access technologies,or may represent partly or entirely different physical components.

FIG. 14 is a block schematic of an exemplary radio network controller orcore network node 1200, in accordance with certain embodiments. Examplesof network nodes can include a mobile switching center (MSC), a servingGPRS support node (SGSN), a mobility management entity (MME), a radionetwork controller (RNC), a base station controller (BSC), and so on.The radio network controller or core network node 1200 include processor1220, memory 1230, and network interface 1240. In some embodiments,processor 1220 executes instructions to provide some or all of thefunctionality described above as being provided by the network node,memory 1230 stores the instructions executed by processor 1220, andnetwork interface 1240 communicates signals to any suitable node, suchas a gateway, switch, router, Internet, Public Switched TelephoneNetwork (PSTN), network nodes 915, radio network controllers or corenetwork nodes.

Processor 1220 may include any suitable combination of hardware andsoftware implemented in one or more modules to execute instructions andmanipulate data to perform some or all of the described functions of theradio network controller or core network node 1200. In some embodiments,processor 1220 may include, for example, one or more computers, one ormore central processing units (CPUs), one or more microprocessors, oneor more applications, and/or other logic.

Memory 1230 is generally operable to store instructions, such as acomputer program, software, an application including one or more oflogic, rules, algorithms, code, tables, etc. and/or other instructionscapable of being executed by a processor. Examples of memory 1230include computer memory (for example, Random Access Memory (RAM) or ReadOnly Memory (ROM)), mass storage media (for example, a hard disk),removable storage media (for example, a Compact Disk (CD) or a DigitalVideo Disk (DVD)), and/or or any other volatile or non-volatile,non-transitory computer-readable and/or computer-executable memorydevices that store information.

In some embodiments, network interface 1240 is communicatively coupledto processor 1220 and may refer to any suitable device operable toreceive input for the network node, send output from the network node,perform suitable processing of the input or output or both, communicateto other devices, or any combination of the preceding. Network interface1240 may include appropriate hardware (e.g., port, modem, networkinterface card, etc.) and software, including protocol conversion anddata processing capabilities, to communicate through a network.

Other embodiments of the network node may include additional componentsbeyond those shown in FIG. 14 that may be responsible for providingcertain aspects of the network node's functionality, including any ofthe functionality described above and/or any additional functionality(including any functionality necessary to support the solution describedabove).

According to certain embodiments, a user equipment is provided for usein a cellular network. The user equipment includes a transceiver, aprocessor, and a memory. The user equipment is configured to determine,for a data transmission, a mapping form a demodulation reference signal(DMRS) to a PNT-RS. A DMRS resulting signal is generated from a subsetof DMRS for a first resource element in a subcarrier. The DMRS resultingsignal is copied from the first resource element to a second resourceelement assigned to the PNT-RS in the subcarrier. The data transmissionis transmitted using the DMRS resulting signal and the PNT-RS.

According to certain embodiments, a method by a user equipment in acellular network includes determining, for a data transmission, amapping form a demodulation reference signal (DMRS) to a PNT-RS. A DMRSresulting signal is generated from a subset of DMRS for a first resourceelement in a subcarrier. The DMRS resulting signal is copied from thefirst resource element to a second resource element assigned to thePNT-RS in the subcarrier. The data transmission is transmitted using theDMRS resulting signal and the PNT-RS.

According to certain embodiments, a network node is provided for use ina cellular network. The network node includes a transceiver, aprocessor, and a memory. The network node is configured to determine,for a data transmission, a mapping form a demodulation reference signal(DMRS) to a PNT-RS. A DMRS resulting signal is generated from a subsetof DMRS for a first resource element in a subcarrier. The DMRS resultingsignal is copied from the first resource element to a second resourceelement assigned to the PNT-RS in the subcarrier. The data transmissionis transmitted using the DMRS resulting signal and the PNT-RS.

According to certain embodiments, a method by a network node in acellular network includes determining, for a data transmission, amapping form a demodulation reference signal (DMRS) to a PNT-RS. A DMRSresulting signal is generated from a subset of DMRS for a first resourceelement in a subcarrier. The DMRS resulting signal is copied from thefirst resource element to a second resource element assigned to thePNT-RS in the subcarrier. The data transmission is transmitted using theDMRS resulting signal and the PNT-RS.

According to certain embodiments, a method in a wireless transmitter forgenerating a PNT-RS includes determining a DMRS and a PNT-RS mapping fora data transmission. A DMRS resulting signal is generated from a subsetof DMRS for a first resource element in a subcarrier. The DMRS resultingsignal signal is copied from the first resource element to a secondresource element assigned to the PNT-RS in the subcarrier. The datatransmission is transmitted using the DMRS resulting signal and thePNT-RS.

According to certain embodiments, a wireless transmitter for generatinga PNT-RS includes a transceiver, a processor, and a memory. The wirelesstransmitter is configured to determine a DMRS and a PNT-RS mapping for adata transmission. A DMRS resulting signal is generated from a subset ofthe DMRS for a first resource element in a subcarrier. The DMRSresulting signal is copied from the first resource element to a secondresource element assigned to the PNT-RS in the subcarrier. The datatransmission is transmitted using the DMRS resulting signal and thePNT-RS.

According to certain embodiments, a method in a wireless receiver fortracking PNT-RS includes performing a first channel estimate on a set ofDMRS in a first Orthogonal Frequency Division Multiplexing (OFDM) symbolin a sub-carrier. A first phase noise reference is determined in a firstresource element in the first OFDM symbol in the sub-carrier. A secondphase noise reference is extracted in a second resource element in asecond OFDM symbol in the sub-carrier. A second channel estimate isgenerated by performing a phase noise compensation of the first channelestimate using said first and second phase reference. Data is receivedin the second OFDM symbol using the second channel estimate.

According to certain embodiments, a wireless receiver for tracking phasenoise tracking reference signal (PNT-RS) includes a transceiver, aprocessor, and a memory. The wireless receiver is configured to performa first channel estimate on a set of demodulation reference signals(DMRS) in a first Orthogonal Frequency Division Multiplexing (OFDM)symbol in a sub-carrier. A first phase noise reference is determined ina first resource element in the first OFDM symbol in the sub-carrier. Asecond phase noise reference is extracted in a second resource elementin a second OFDM symbol in the sub-carrier. A second channel estimate isgenerated by performing a phase noise compensation of the first channelestimate using said first and second phase reference. Data is receivedin the second OFDM symbol using the second channel estimate.

Certain embodiments of the present disclosure may provide one or moretechnical advantages. For example, certain embodiments may enable anoverhead reduction and better utilization of resources for DMRS,enabling a high number of DMRS early in a sub-frame even in the presenceof a substantial number of orthogonal PNT-RS. There is no other knownsolution when using all resource elements in an OFDM symbol for DMRSwhile enabling phase noise tracking. Consider, for example, an uplink(UL) (or downlink (DL)) Multi User Multiple Input Multiple Output(MU-MIMO) system with four or more receiver antennas. Therefore, thebenefits of having only DMRS in an OFDM symbol such as better peak toaverage and nice frequency interpolation properties, frequency domaincombs are blocked without the herein disclosed systems and techniques.

Modifications, additions, or omissions may be made to the systems andapparatuses described herein without departing from the scope of thedisclosure. The components of the systems and apparatuses may beintegrated or separated. Moreover, the operations of the systems andapparatuses may be performed by more, fewer, or other components.Additionally, operations of the systems and apparatuses may be performedusing any suitable logic comprising software, hardware, and/or otherlogic. As used in this document, “each” refers to each member of a setor each member of a subset of a set.

Modifications, additions, or omissions may be made to the methodsdescribed herein without departing from the scope of the disclosure. Themethods may include more, fewer, or other steps. Additionally, steps maybe performed in any suitable order.

Although this disclosure has been described in terms of certainembodiments, alterations and permutations of the embodiments will beapparent to those skilled in the art. Accordingly, the above descriptionof the embodiments does not constrain this disclosure. Other changes,substitutions, and alterations are possible without departing from thespirit and scope of this disclosure, as defined by the following claims.

1. A user equipment for use in a cellular network, the user equipmentcomprising a transceiver, a processor, and a memory, the user equipmentconfigured to: determine, for a data transmission, a mapping form ademodulation reference signal (DMRS) to a PNT-RS; generate a DMRSresulting signal from a subset of DMRS for a first resource element in asubcarrier; copy the DMRS resulting signal from the first resourceelement to a second resource element assigned to the PNT-RS in thesubcarrier; and transmit the data transmission using the DMRS resultingsignal and the PNT-RS.
 2. The user equipment of claim 1, wherein thefirst resource element is associated with a first Orthogonal FrequencyDivision Multiplexing (OFDM) symbol, and wherein all resource elementsassociated with the first OFDM symbol are used for the DMRS resultingsignal.
 3. The user equipment of claim 2, wherein the second resourceelement is associated with a second OFDM symbol.
 4. The user equipmentof claim 1, wherein the PNT-RS is continuous in all OFDM symbols of thesubcarrier.
 5. The user equipment of claim 4, wherein copying the firstresource element comprises copying a complex value from the firstresource element to each of the OFDM symbols of the subcarrier mapped tothe PNT-RS.
 6. The user equipment of claim 5, wherein each copy of thecomplex value is time shifted across the OFDM symbols of the subcarriermapped to the PNT-RS, wherein each copy is shifted with a CP duration.7. The user equipment of claim 1, wherein: the DMRS resulting signal isgenerated using Orthogonal Cover Code (OCC) of a length comprising aplurality of adjacent OFDM symbols; and wherein copying the DMRSresulting signal comprises for each one of the plurality of adjacentOFDM symbols, copying a respective DMRS resulting into a respectiveOFDM-symbol.
 8. The user equipment of claim 1, wherein the transceivercomprises a multi-antenna receiver.
 9. The user equipment of claim 1,wherein the transceiver comprises a multi-antenna transmitter.
 10. Amethod by a user equipment in a cellular network, the method comprising:determining, for a data transmission, a mapping form a demodulationreference signal (DMRS) to a PNT-RS; generating a DMRS resulting signalfrom a subset of DMRS for a first resource element in a subcarrier;copying the DMRS resulting signal from the first resource element to asecond resource element assigned to the PNT-RS in the subcarrier; andtransmitting the data transmission using the DMRS resulting signal andthe PNT-RS. 11.-18. (canceled)
 19. A network node for use in a cellularnetwork, the network node comprising a transceiver, a processor, and amemory, the network node configured to: determine, for a datatransmission, a mapping form a demodulation reference signal (DMRS) to aPNT-RS; generate a DMRS resulting signal from a subset of DMRS for afirst resource element in a subcarrier; copy the DMRS resulting signalfrom the first resource element to a second resource element assigned tothe PNT-RS in the subcarrier; and transmit the data transmission usingthe DMRS resulting signal and the PNT-RS.
 20. The network node of claim19, wherein the first resource element is associated with a firstOrthogonal Frequency Division Multiplexing (OFDM) symbol, and whereinall resource elements associated with the first OFDM symbol are used forthe DMRS resulting signal.
 21. The network node of claim 20, wherein thesecond resource element is associated with a second OFDM symbol.
 22. Thenetwork node of claim 19, wherein the PNT-RS is continuous in all OFDMsymbols of the subcarrier.
 23. The network node claim 22, whereincopying the first resource element comprises copying a complex valuefrom the first resource element to each of the OFDM symbols of thesubcarrier mapped to the PNT-RS.
 24. The network node of claim 23,wherein each copy of the complex value is time shifted across the OFDMsymbols of the subcarrier mapped to the PNT-RS, wherein each copy isshifted with a CP duration.
 25. The network node of claim 19, wherein:the DMRS resulting signal is generated using Orthogonal Cover Code (OCC)of a length comprising a plurality of adjacent OFDM symbols; and whereincopying the DMRS resulting signal comprises for each one of theplurality of adjacent OFDM symbols, copying a respective DMRS resultinginto a respective OFDM-symbol.
 26. The network node of claim 19, whereinthe transceiver comprises a multi-antenna receiver.
 27. The network nodeof claim 19, wherein the transceiver comprises a multi-antennatransmitter.
 28. A method by a network node in a cellular network, themethod comprising: determining, for a data transmission, a mapping forma demodulation reference signal (DMRS) to a PNT-RS; generating a DMRSresulting signal from a subset of DMRS for a first resource element in asubcarrier; copying the DMRS resulting signal from the first resourceelement to a second resource element assigned to the PNT-RS in thesubcarrier; and transmitting the data transmission using the DMRSresulting signal and the PNT-RS. 29.-70. (canceled)